1. Field of the Invention
The present invention relates to an apparatus for imaging, recording, and reproducing a still image.
2. Description of the Related Art
An electronic still camera which can cause an image sensor to convert an object image into an electrical image signal, can record this image signal in a recording medium, and which has a reproduction circuit, has bee developed in place of a conventional optical camera using a silver chloride film.
A conventional example of a still camera of this type is shown in FIG. 8.
In this conventional electronic still camera, an object is imaged through a lens 100 and a shutter 101, and an optical image is guided to an image sensor 102 and is converted therein into a charge image. The charge signal is read in synchronism with a sync signal generated by a sync signal generator (SSG) 122 under the control of an image sensor drive circuit 102-1. A motor 112 is controlled by a servo circuit 113 in synchronism with the sync signal from the SSG 122. Upon completion of rotation control, a sync completion signal is supplied to a system controller 123. The system controller 123 supplies a read command to the SSG and the image sensor drive circuit in response to the sync completion signal in order to read image data.
R, G, and B analog data of the read pixels are amplified by an amplifier 103, and the amplified signals are converted into a luminance signal and chrominance signals (color difference signals in this case) by a matrix circuit 104. The chrominance signals are switched by a switch 130 in units of horizontal lines by a switching signal from the SSG 122 so as to be converted into line sequential signals of a still image format. The switched chrominance signals are supplied to a low-pass filter 106. The luminance signal Y is added to a sync (horizontal/vertical) sync signal from the SSG 122 by an adder 105-1, and luminance signal components except for the modulation band are eliminated by a low-pass filter 105. The chrominance line sequential signal wave is modulated by a modulator 108 and added to the modulated wave of the luminance signal by an adder 107-1, so that modulated waves of the chrominance signals are frequency-multiplied, and an output from the adder 107-1 is amplified to an optimal recording level by an amplifier 109.
The signal output from the amplifier 109 is supplied to a recording head 130 through a switch 135 and is concentrically recorded in a recording medium 131. Reference numeral 110 denotes a carrier for radially moving the recording head 130. The above operations include the image sensing process to the recording process.
To reproduce recorded signals, the head 130 is moved to a recorded track by the head carrier 110, and an image signal recorded by the magnetic head 130 is converted into an electrical signal. The electrical signal is supplied to a reproduction amplifier 115 through the switch 135. The signal is then supplied to a band-pass filter 116 and a low-pass filter 117. Outputs from the filters 116 and 117 are input to FM demodulators 118 and 119, respectively. Outputs from the FM demodulators 118 and 119 serve as baseband signals for the luminance and chrominance signals, respectively. The servo circuit 113 compares the phase of a reference signal from the SSG 122 with that of an FG signal from a motor and generates an error signal. The motor 112 is rotated at a speed corresponding to the reproduction signal by using the error signal from the servo circuit 113. As described above, the reproduction image is stabilized, and the chrominance signals are line sequential signals and are synchronized by a line sync circuit consisting of a switch 136 and a line sense circuit 137. The chrominance signals and the luminance signal are converted into an NTSC signal by an NTSC encoder.
In the circuit arrangement described above, the motor 112 must be quickly rotated and stabilized until it is synchronized with the reference signal from the SSG 122 during a time interval from depression of a release button 138 for photography to depression of a shutter button 139. A motor having excellent rise characteristics must be used. When the motor quickly rises, instantaneous power consumption is increased, and a battery capacity must be large. In the conventional circuit arrangement, power consumption is large when the line sync circuit is operated in the reproduction mode and a skew compensator is operated in the field reproduction mode since -h delay lines are used. In addition, in a reproduction image monitor mode, the motor must always be rotated further increasing the power consumption. A reproduction time is shortened when a battery capacity is small as compared with a recording camera without any reproduction function, thus posing a significant problem.